The present invention relates to a video signal receiving apparatus including a television receiver having a receiving mode for cable television, for example. The present invention also relates to a video signal receiving system containing the above-mentioned video signal receiving apparatus.
A cable television (CATV) system is known that retransmits television and FM broadcasting programs in VHF and UHF broadcasting frequency bands and transmits local community broadcast, satellite broadcast, and other television broadcast programs in the midband and super highband of the frequency band to distribute the programs to many subscribers through transmission media such as coaxial cables.
A receiving apparatus and a sending apparatus for television broadcasting and satellite broadcasting are closely arranged at a center station (or a head end) of the CATV system by which many channels of television signals sent at suitable levels are distributed to the subscribers through a relay transmission path called a trunk system and a distribution system with a distributing apparatus (or a tap-off) composed of a passive element connected with an output of a high-power amplifier.
As mentioned above, since multi-channel signals are transmitted in the CATV system, an ordinary television receiver cannot receive all the channels. Therefore, each of the subscribers is supplied with a receiving terminal (or a cable box) having a tuner capable of receiving multiple channels according to a contract concluded with a CATV broadcasting company on a lease or buy basis. Using this cable box, each subscriber receives television signals of desired CATV channels.
In this case, a television signal received and tuned in with the cable box is converted by an RF converter into a broadcast wave of an idle channel of the television receiver, the resultant broadcast wave being supplied to an antenna input terminal of the television receiver. The audience can tune in the idle channel of the television receiver to view the CATV broadcast.
In a case where the cable box has output terminals for a demodulated video signal and a demodulated sound signal obtained from the received and tuned in television signal and the television receiver has input terminals for the video and sound signals, the output terminals of the cable box are connected to the input terminals of the television receiver. In that case, an input selector of the television receiver is put in a state for selecting the input terminals, allowing the audience to view the CATV broadcast.
It should be noted that, in CATV, pay broadcast programs such as pay television and pay per view are scrambled to prevent free viewing, so that the above-mentioned cable box is provided with a descrambler.
In addition, it is a general practice with recent television receivers that user input operations for operational control such as channel selection and input selector selection are performed on a remotely controlled operator unit (hereinafter referred to as a remote commander) to send a remote control signal from the remote commander to a remote control signal receiving portion of the television receiver in a wireless manner using an infrared ray or other means.
Likewise, the cable box also has a remote control signal receiving portion in many cases. In this case, channel selection, for example, is performed by means of a remotely controlled tuning control signal sent from the remote commander in a wireless manner.
Thus, the cable box can be remotely controlled by a remote commander as with the television receiver. Therefore, if operations such as channel tuning control can be performed at the cable box by means of a remote commander for the television receiver, the remote commander can be shared by both the cable box and the television receiver to construct a video signal receiving system having a remote control system that is extremely easy to use.
However, generally the manufacturers of the cable box and the television receiver are different, so that the remote control signal for the cable box is different from the remote control signal of the television receiver in format, thereby making it impossible to use the same remote commander for the television receiver as the cable box.
To solve this problem, a system is proposed in which an output terminal 1c for the remote control signal is provided on a television receiver 1 as shown in FIG. 16, the output terminal 1c being connected to a transmitter 2 for controlling external apparatus to transmit a remote control signal RC for a cable box 3 from the transmitter 2 to the cable box 3 in a wireless manner.
That is, referring to FIG. 17, in the television receiver 1, a remote control signal received by a remote control signal coming from a remote commander 4 and received portion 1R is decoded by a control microcomputer 1M. Based on the decoding result, a control signal is supplied to each portion of the television receiver 1. The remote control signal coming from the remote commander 4 and received by the remote control signal receiver 1R is output to a remote control signal output terminal 1c directly. It should be noted that the remote control signal receiver 1R shapes the remote control signal coming from the remote commander 4 before reproducing an original remote control signal waveform.
The transmitter 2 for controlling external apparatus decodes the remote control signal coming from the output terminal 1c by means of a decoder 2D, then converts the decoded control signal to a remote control signal for the cable box by means of a converter 2H, and transmits the converted control signal to a remote control signal receiver 3R of the cable box 3 in a wireless manner.
In the receiving system thus constituted, it is possible, by means of the remote commander 4, to select, in the cable box 3, a television signal of one of multiple channels coming via a CATV cable 5.
However, as mentioned above, since the television receiver used in the conventional video signal receiving system has a constitution in which the remote control signal coming from the remote commander 4 is output to the output terminal 1c without change to be sent to the transmitter 2 for controlling external apparatus, the cable box 3 is supplied only with a key signal directly corresponding to each operator button on the remote commander; for example, if a numeric key is operated, a key signal that indicates the operation is supplied to the cable box.
Consequently, it has been impossible to implement composite channel operating capabilities using the control microcomputer 1M unless the capability is provided on the cable box.
That is, a predetermined channel corresponding to a predetermined number is preset in memory by a user as a channel to be frequently viewed for example, and the preset channel is put in a read mode. Then, when the corresponding number is entered from a numeric key, the desired predetermined channel can be selected.. However, with a cable box not having such a capability, a key input on the remote commander for setting the mode for reading the preset channel is ignored and only a subsequent numeric key input is made valid, thereby selecting a channel corresponding the subsequent key operation.